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Summary Aim To assess the effects of water immersion on cardiovascular requirements, 30 min immersed versus air steady exercises at neutral temperature were compared in two settings:similar energy expenditure (60% maximal oxygen consumption; series 1) and similar ergometric workload (120 W; series 2). For 15 healthy male subjects, the arterial blood pressure, heart rate, thoracic fluid conductivity (TFC), cardiac index (CI) and stroke index (SI) were monitored at rest, during the exercise period and during 30 min of post-exercise recovery in two conditions. Plasma atrial natriuretic peptide (ANP) was also measured. Results Resting water immersion increased TFC, CI, SI, and systolic arterial pressure (SAP). During exercise the average CI, SI and SAP were not different in water and air in series 1, but in series 2 CI, SI, heart rate, systolic and diastolic arterial pressures were higher in water. Plasma ANP was higher after immersed exercises. During recovery, CI was similar after either exercise, while SI was lower and heart rate higher following immersion, consistent with a lower effective circulatory volume than after exercise in air. TFC was high, as reflecting an increased interstitial fluid content in the lung. Conclusions Cardiovascular requirements for exercising in water were markedly higher than in air and straining of lung parenchyma. |
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